Many chromosomal and metabolic diseases of the fetus could be diagnosed before birth. Investigations could be performed if we are able to obtain fetal cells. One of the methods widely used for this purpose is amniocentesis. Amniocentesis is a minor surgical procedure during which a fine needle is inserted through the abdominal wall into the amniotic sac and a small amount of amniotic fluid is aspirated. The fetal cells from the amniotic fluid are cultured and chromosomal or biochemical investigations are performed. The results are available in about three weeks.
A new method call chorion biopsy is used in many centres and in some of them is offered as a procedure of choice. To obtain chorion tissue a small diameter tube is inserted into the uterine cavity through the cervical canal and by aspiration a small amount of chorion tissue is obtained. Chromosomal investigations could be done immediately and the results could be ready in a day or two.
Amniocentesis is usually done at about fourteen weeks gestation and when the results are available from the investigations the pregnancy will reach 17-18 weeks gestation. If the fetus is abnormal, mid-trimester abortion could be performed. However, this carries a risk of infection and bleeding, very rarely even death.
Chorion biopsy can be performed early in pregnancy, between 8 and 12 weeks gestation, and if an abnormal fetus is discovered the pregnancy can be interrupted by suction curretage. This is a much simpler and safer operation than a mid-trimester abortion.
One of the simplest and most widely used instruments consists only of a tube with a small diameter to which a syringe is attached. After the tube is inserted into the uterine cavity and suction is created, chorion tissue enters the tube. In order to obtain chorion tissue, the tube and the attached syringe are pulled out of the uterine cavity. A piece of chorion is usually retained in the tube. After the tube is taken out, it is irrigated and the chorion which is trapped inside is removed. If chorion has not been obtained, which is very often, the tube has to be reinserted.
There are optical instruments which have a guillotine-type cutting mechanism, the disadvantage of which is that the diameter is usually large and therefore insertion is not always easy. This causes trauma to the uterus and to the fetus. Another disadvantage is that the optical part becomes blurry due to bleeding that occurs during intrauterine manipulation. After the suction is applied and the tissue is cut, the whole instrument has to be removed in order to retrieve the chorion tissue. If the procedure is unsuccessful, the instrument has to be reinserted.
A chorion biopsy can also be performed by using grasping forceps. This is a very crude procedure which often perforates the membranes and causes abortions.
Consequently, there is a need for an improved chorion biopsy instrument.